MORE embryology

Question 1

type 2 pneumocytes cell type and function

Answer 1

cuboidal cells
secrete surfactant (from lamellar bodies) to increase surface tension

Question 2

type 2 pneumocytes are precursors to…

Answer 2

type 1 pneumocytes
or can become other type 2

Question 3

collapsing pressure of an alveolus

Answer 3

(2 x surface tension) divided by radius

Law of laplace is wall stress = P x r / 2w
(w is wall thickness)

Question 4

week ?? = surfactant synthesis begins
week ?? = mature levels of surfactant

Answer 4

week 26 = surfactant synthesis begins
week 35 = mature levels of surfactant

Question 5

what are Clara cells / club cells / bronchiolar exocrine cells

Answer 5

protects

Question 6

what is the lecithin–sphingomyelin ratio (or L-S ratio)

Answer 6

lecithin–sphingomyelin ratio is a marker of fetal lung maturity
=/> 2.4 indicates maturity
</= 1.5 high risk of RDS

taken from amniotic fluid - the outward flow of pulmonary secretions from the fetal lungs into the amniotic fluid maintains the level of lecithin and sphingomyelin equally until 32–33 weeks gestation, when the lecithin concentration begins to increase significantly while sphingomyelin remains nearly the same

Question 8

what is the main component of surfactant?

Answer 8

DPPC
di-palmitoyl-phosphatidyl-choline

Question 9

In lung development, when is histological ‘pseudoglandular’ stage
what structures have formed in that time?

Answer 9

is 5 - 17 weeks (or 6-16, which makes the next stage easier to remember as it is 16 - 26)

bronchioles and terminal bronchioles

pseduoglandular stage (when histologically it looks like a gland, with cuboidal cells, a few vessels and some connective tissue)

Question 10

which does gas exchange - bronchioles, terminal bronchioles, respiratory bronchioles

Answer 10

respiratory bronchioles only. Ridiculous that ‘terminal’ isn’t really the last type, but at least ‘respiratory’ does what is says on the tin

Question 11

In lung development, when is histological ‘canalicular’ stage
what structures have formed in that time?

Answer 11

16 - 26 weeks
respiratory bronchioles and alveolar ducts
plus, the terminal bronchioles and higher start to widen (canals of canalicular stage!)

Question 12

In lung development, when is histological ‘saccular’ stage
what structures have formed in that time?

Answer 12

26+ weeks
alveolar sacs (‘saccular’ stage) form and SURFACTANT starts to be made

Question 13

In lung development, when is histological ‘alveolar’ stage
what structures have formed in that time?

Answer 13

bit of a trick question - it’s birth to 8 years
lots and lots of alveoli

Question 14

the palate is derived from what embryological structure

Answer 14

1st pharangeal arch (maxillary)

Question 15

where is fetal AFP principally produced

Answer 15

Liver

Question 16

The ectoderm and endoderm remain in contact, without intervening mesoderm, in which two regions

Answer 16

the buccopharyngeal membrane and the cloacal membrane.

Question 17

Schwann cells and meninges are derived from…

Answer 17

neural crest cells
(meninges are also a bit mesenchymal)

Question 18

The liver develops as an outgrowth of the endoderm of the distal foregut, as does the gall bladder, bile and cystic ducts.
BUT, the haemopoietic cells, Kupffer cells and connective tissue are derived from…

Answer 18

the mesoderm of the septum transversum

Question 19

regarding development of the pancreas, the dorsal bud becomes…
the ventral bud becomes…

Answer 19

dorsal - head, body, tail
ventral - uncinate process

Question 20

when does the foetal pancreas start to secrete insulin

Answer 20

5th month

Question 21

which week of gestation does the midgut do its rotation?

Answer 21

6th week (according to notes I was given)

Question 22

During which week, the midgut retracts into the abdomen, undergoing a further 180 degrees
rotation

Answer 22

10th (according to notes I was given)

Question 23

when does the gut tube occlude?
when does it recanalise?|
what phenomena occur if there are issues with this process?

Answer 23

week 5.
week 9 (w7 starts recanalising, finished by week 9).
stenoses.

As the gut tube tube develops, the endoderm proliferates rapidly and actually temporarily OCCLUDES the lumen of the tube around the 5th week. Growth and expansion of mesoderm components in the wall coupled with apoptosis of some of the endoderm at around the 7th week causes re-canalization of the tube such that by the 9th week, the lumen is open again.
This occlusion and re-canalization process occurs THROUGHOUT the tube (esophagus to anus) and errors in this process can occur in anywhere along the tube resulting in stenosis (narrowing of the lumen or even outright occlusion) in that region.

Question 24

which 4 structures are secondarily retroperitoneal?

Answer 24

pancreas
duodenum (both foregut and midgut-derived portions)
ascending colon
descending colon

Question 25

what is the remnant of the notochord?

Answer 25

the nucleus pulposus of the intervertebral discs

Question 26

what is the function of the notochord

Answer 26

it runs the longitudinal length of the embryo and sends out SHH to tell other cells where they need to go to do their thing!

Question 27

embryonic age is how many weeks shorter than gestational age? Why is this?

Answer 27

GA is 2 weeks longer than embryonic age as it is from the first day of the LMP, as that's what you can be certain of, as the woman, and not fertilisation day, I suppose!

Question 28

when does the embryo begin sexual differentiation

Answer 28

week 7

Question 29

when does the heartbeat start

Answer 29

week 4 (day 22-23)

Question 30

when does sex of fetus become recognisable on USS

Answer 30

week 10 - 12

Question 31

when does the mesonephros regress in the female

Answer 31

week 10

Question 32

when does gonadal development begin, with the formation of the gonadal ridge?

Answer 32

week 5

Question 33

between which weeks does the metanephros become the permanent kidney?

Answer 33

weeks 5 - 15 (but is functional from week 10)

Question 34

what is the origin of the ureters

Answer 34

ureteric bud, an outgrowth of the MESOnephric duct (i.e. the same duct that makes the male genital tract, but NOT the same one that makes the bulk of the kidney - that's the metanephric duct) It's the ureteric bud being absorbed into the bottom of the bladder that means the trigone is mesodermal in origin, not endodermal

Question 35

What has to be present for the definitive kidney to form

Answer 35

the definitive kidney is from the METAnephric duct but the ureteric bud is from the MESOnephric duct The metanephric mesoderm develops into the Bowmans capsule etc. UNDER THE INFLUENCE OF THE URETERIC BUD. So if the ureteric bud is missing, the kidney does not develop.

Question 36

what is the embryological origin of Sertoli and Leydig cells

Answer 36

Sertoli are from the sex cords leydig are from the mesenchyme

Question 37

what are the stages of development of the structure from gonadal ridge (end of week 6) to seminiferous tubules?

Answer 37

gonadal ridge primitive sex cords medullary cords (with sertoli cells, make Mullerian Inhibitory Factor) the medullary cords remain solid until puberty when they become canalised, forming the seminiferous tubules

Question 38

When does the first meiotic division of the primary spermatocyte occur

Answer 38

puberty

Question 39

describe the origin of the accessory glands of the male reproductive system

Answer 39

seminal vesicles from mesonephric duct (mesoderm) prostate from prostatic urethra (from urogenital sinus - endoderm?) bulbourethral glands also from urogenital sinus

Question 40

the testes are in the inguinal region in the 12th week of development. When do they reach the scrotum?

Answer 40

The final descent of the testis into the scrotum occurs in the 7th-9th MONTHS (due to the relative growth of the body compared to the gubernaculum)

Question 41

The processus vaginalis is obliterated, forming the tunica vaginalis. When does this happen?

Answer 41

during the first year of life

Question 42

The umbilical vein carries ?ated blood from the ? to the ?

Answer 42

The umbilical vein carries oxygenated blood from the placenta to the fetus

Question 43

Oxygenated blood in the umbilical vein bypasses the ?, draining into the ? via the ?

Answer 43

Oxygenated blood in the umbilical vein bypasses the liver, draining into the inferior vena cava via the ductus venosus

Question 44

The obliterated umbilical vein forms the ligamentum ? while the obliterated ductus venosus forms the ligamentum ?

Answer 44

umbilical vein --> teres ductus venosus --> venosum

Question 45

Oxygen saturation in the umbilical arteries (taking blood from baby to placenta)

Answer 45

58%

Question 46

The proximal part of the umbilical arteries form the ?. The obliterated distal part form the ?

Answer 46

The proximal part of the umbilical arteries form the superior vesical arteries. The obliterated distal part form the mediAL umbilical ligaments

Question 47

In the fetus, is the blood in the SVC oxygenated or deoxygenated

Answer 47

it's deoxygenated! Because the umbilical vein connects with the IVC (not the SVC) although the IVC will still also be draining blood from the body, as well as getting blood from the placenta, so it's not 100% oxygenated. so the SVC is carrying deoxygenated blood back from being used in the baby's body

Question 48

how long does obliteration of the umbilical arteries take?

Answer 48

functionally closed within a few minutes of birth, obliteration takes 2-3 months EXCEPT the proximal portion of the umbilical arteries which form the superior vesical arteries

Question 49

most of the embryonic vascular ducts close with the first breath due to the change in pressure and resistance. However, what does the ductus arteriosus require to close?

Answer 49

DA closure is dependent on a rise in PaO2. Hypoxia in neonatal period can cause it to become patent!

Question 50

what does the 2nd pharyngeal POUCH make?

Answer 50

palatine tonsil

Question 51

when does the sinovaginal bulb become canalised to form the vagina?

Answer 51

end of the 5th month

Question 52

haemopoietic cells, Kupffer cells and connective tissue of the liver are from mesoderm (the rest is endoderm). What are Kupffer cells?

Answer 52

Kupffer cells are specialized macrophages in the liver that phagocytose foreign substances and bacteria

Question 53

vitelline duct connects what structures?

Answer 53

yolk sac and midgut